The invention relates to a magnetic head, and more particularly to a magnetic head in which the abutting ends of a pair of core pieces and a yoke which are adhesively secured together are retained in position by a bobbin on which a coil is wound.
Referring to FIG. 1 for a brief description of a conventional monoaural magnetic head, it comprises a pair of core pieces 1, 2, which are joined together with a spacer 3 inteposed therebetween to define a gas l.sub.0. A pair of coils 4, 5 are wound on a pair of bobbins 6, 7, which are fitted on a pair of arms 8a, 8b of a yoke 8 which interconnects the opposite ends of the core pieces to complete the magnetic path. End faces 8c, 8d of the arms 8a, 8b of the yoke 8 are polished to a mirror finish as are the end faces 1a, 2a, of the core pieces 1, 2 which are located remote from the gap, and these end faces are applied with an adhesive and brought into abutting engagement against each other, thus adhesively securing the core pieces and the yoke together.
FIG. 2 shows a conventional magnetic head adapted for use with a two channel magnetic tape. Tjhe head includes a pair of core pieces 101, 102 which are joined together with a spacer 103 interposed therebetween to define a gap l'.sub.0. A pair of coils 104, 105 are wound on a pair of bobbins 106, 107, which are in turn fitted on a pair of arms 108a, 108b of a yoke 108 which interconnects the both core pieces to complete the magnetic path thereof. The yoke 108 has a pair of end faces 108c, 108d, which are polished to a mirror finish as are end faces 101a, 102a of the core pieces 101, 102 which are located remote from the gap. These end faces are brought into abutting engagement and adhesively secured together to form a monoaural magnetic head 109a. Similarly another monoaural magnetic head 109b is formed, and these heads 109a, 109b are stacked one above the other with a shielding plate 110a interposed therebetween.
In these magnetic heads, the spacer comprises beryllium bronze when the core pieces comprise permalloy, and comprise fused glass where the core pieces comprise ferrite. It will be noted that in FIGS. 1 and 2, the bobins 6, 7 are provided with terminals 9, 10 for the coils 4, 5, and the bobbins 106, 107 are provided with terminals 111a, 111b for the coils 104, 105, respectively.
When adhesively securing the core and the yoke together, the use of a so-called flash adhesive will achieve a high efficiency, but may frequently result in a poor adhesion. While adhesives such as epoxy resin which becomes hardened on heating may be used, there remains the possibility of a burn-out of the coils. To avoid these difficulties, an aged hardening of adhesives such as epoxy resis has been frequently employed. However, in this instance, the portions of the core and the yoke which are to be bonded together must be maintained in abutment against each other and prevented against unintended movement by means of some retaining members for a period of 12 hours or longer until the hardening is complete. Such a retaining member generally has an increased size, and since one retaining member is required for each monaural head, its use presented problems in the manufacturing in terms of the cost and space requirement. Since the core and the yoke cannot be moved during the process of hardening, they cannot be carried into the next step, so that the aged hardening does not lend itself to a mass production.